Business is in the business to win the jackpot, especially when their dream is to make big bucks off them cultural events.
Now if daddy needs a new tacoma or the day before, the family lost big bucks at the casino, how else do you think they will recoup their lost?
There should be some kind of an organization control, like a government base run for you guy's event by saying something like if they want to sell at your event, the prices should be affordable and controlled so that the event will prosper even more. Imagine if $5 for a box of sticky rice and meat, $5 for everything. What vendor can do is to cut the portion down to $5 worth. Who doesn't like to go to flea market where people go because of the price?